This invention relates generally to robots. More specifically, it relates to robots of the type which are commonly referred to as pick and place robots.
Pick and place robots are used in material handling applications where it is desired to move an object from one place to another by grasping the object, moving the object, and then releasing the object.
There are many known types of pick and place robots. Some are relatively simple devices, others are more sophisticated.
The robot of the present invention is particularly, although not exclusively, adapted for moving objects in a confined space with specific rotational control.
In the disclosed application of the present invention in a storage/retrieval system, the robot is disposed in a confined space between a pair of confronting storage units which have a number of unique storage locations for palleted articles. The robot is operable to store a palleted article by grasping it at a point of ingress to the system, moving the article to a desired storage location in one of the storage units, and then releasing it at that location. When an article is to be retrieved from storage, the robot picks it up at its storage location, moves it to a point of egress from the system, and then releases it. The disclosed system has a common ingress/egress point. It is also possible for the robot to rearrange the stored articles within the storage units.
Each of the storage units comprises a series of horizontal storage shelves which are disposed at intervals along the length of an endless vertical track. The storage shelves are coupled for travel in unison along the track while at all times remaining horizontal to support any articles which have been placed upon them. The endless vertical track consists of two vertical segments joined at respective ends by semi-circular segments. One of the two vertical segments of each storage unit's track is toward the front of the unit, and the two units are arranged so that their fronts face each other across the confined space where the robot is located. Articles are stored and retrieved via openings in the fronts of the storage units. Each storage shelf is compartmentalized into a number of individual storage compartments so that each compartment can store one pallet. Greater detail of these particular storage units will be presented later on in the description.
The robot is arranged for horizontal longitudinal travel parallel to the lengths of the shelves, and for this purpose comprises parallel guides which extend in that direction and a carrier which travels on the guides. The two storage units are equidistant from the path of carrier travel.
An arm which has a gripper mechanism at its distal end is supported on the carrier. The particular form of gripper mechanism will depend upon the nature of the particular articles which are to be handled. In the illustrated embodiment, it comprises a pair of spaced apart tines which are operable for engagement with generally rectangular shaped pallets.
The arm is supported on the carrier by a mechanism which enables the arm to be: (1) vertically raised and lowered relative to the carrier; (2) to be rotated about a vertical axis; and (3) to be displaced horizontally along a radial relative to the vertical axis of rotation.
Accordingly, the combined carrier and arm motions constitute the robot a four-axis mechanism capable of three linear motions and one rotational component, all independent. Certain principles of the invention however may be adapted to other than four-axis designs.
One of the outstanding attributes of the invention is that it can fit and operate within the laterally confined space between the two confronting storage units of the type described, while simultaneously being able to accurately position the gripper mechanism, particularly with reference to rotational positioning about the vertical axis, and with the ability to handle relatively heavy loads.
In the illustrated embodiment of the invention, the point of ingress and egress of a palleted article to and from the storage system lies adjacent one end of the horizontal longitudinal travel of the carrier, just beyond the storage units. When the robot is to store an article, it extends its arm to grasp the article at the point of ingress and egress. It then moves the article horizontally in the longitudinal direction so as to bring the article between the two storage units, and it also rotates the arm, either clockwise or counterclockwise depending upon which storage unit is to receive the article, so as to position the grasped article in front of a particular storage location. The arm then extends to place the article at the desired storage location and to release it.
Because a gripped article is disposed at an extended radial distance from the vertical axis of rotation, small angular errors in rotational positioning can be amplified into significant errors in longitudinally locating the article in relation to the desired storage location, even with extreme accuracy in positioning of the carrier. The problem is compounded when relatively heavy articles are being handled.
One of the important features of the present invention is that the robot mechanism is capable of reducing such rotational positioning errors essentially to zero. In the disclosed embodiment this is accomplished by a unique mechanism which includes adjustable stops cooperatively associated with a rack and pinion mechanism operated by a cable cylinder to define precise stopping locations correlated with precise positioning of the articles, yet which allows the robot to serve the two confronting storage units within the laterally confined space between them, and to access the point of ingress and egress.
Moreover, the robot comprises a construction and arrangement which maintains vertical accuracy, despite the imposition of substantial loads acting at an appreciable distance from the axis of rotation. In other words, the torque which is imposed on the vertical axis due to the support of a heavy load at an extended distance is well-accomodated and does not impair the accuracy of the positioning while the robot's arm moves the heavy load.
The arrangement of operators for imparting the various motions to the robot is also advantageous, contributing to the robot's compactness, yet endowing it with the ability to move relatively heavy loads with accuracy and speed.
The robot and storage/retrieval system is adaptable to a computer-based control where identities of articles and their storage locations are electronically recorded, and articles are stored, retrieved, or re-arranged within storage under computer control.
The foregoing features, advantages, and benefits of the invention, along with additional ones, will be seen in the ensuing description and claims which should be considered in conjunction with the accompanying drawings. The drawings disclosed a preferred embodiment of the invention according to the best mode contemplated at the present time in carrying out the invention.